Method for qualitative and quantitative multiplexing of drug analytes from biological samples

A method for qualitative and quantitative multiplexing of drug analytes from dried blood samples includes the steps of mixing an Internal Standard solution with a first diluent in a vessel, adding the dried blood sample to the vessel, sonicating the vessel containing the Internal Standard solution, the first diluent and the dried blood sample, removing the dried blood sample from the vessel so that a final sample can be attained, and analyzing at least a portion of the final sample using one of LC-MS and LC-MS/MS to simultaneously determine the presence or absence of a plurality of different analytes in the dried blood sample. The Internal Standard solution can include at least 8, 15, 25 or 50 Internal Standards. The dried blood sample is generated using less than 50 μL, 20 μL or 10 μL of blood. The step of analyzing includes simultaneously determining the presence or absence of at least 15, 60, 90 or 130 different analytes. A ratio of the number of analytes for which the presence or absence is being determined to the number of Internal Standards in the Internal Standard solution is at least approximately 2:1. A ratio of the number of analytes for which the presence or absence is being determined to the volume (in μL) of the final sample being analyzed is at least approximately 2:1. A ratio of the number of analytes for which the presence or absence is being determined to the volume (in μL) of blood from which the dried blood sample was obtained is at least approximately 4:5.